I had two dwarf puffers, I started off with some ottos and them, they were living happily except for the occasional nipping from the puffers and one day POOF ottos gone never found them, so just be aware. Thought I would warn you as ottos are quite pricey. My puffers ate any size snails even the ones I thought was too big, they would just vigorously nip on the until they were empty, another friendly warning, feed only snails when they need them as food, do not think you can put 20+ in the tank to breed while they are in there, they assasinate the lot and only eat some of them when they get hungry LOL
Just sharing my experience with them. I learned they are a fish only species, any other fish is food, even big bristlenoses.